An active matrix substrate is widely used for various active matrix display apparatuses such as a liquid crystal display apparatus, an EL (Electro Luminescence) display apparatus etc. In an active matrix substrate used for a conventional active matrix liquid crystal display apparatus, a switching element such as a TFT (Thin Film Transistor) is provided in each intersection of a plurality of scanning signal lines and a plurality of data signal lines which are intersect with each other on a base substrate. With the switching function of this switching element such as a TFT, each pixel (electrode) of pixel section connected to the switching element (eg. TFT) is supplied with a pixel signal according to circumstances. Further, there is a kind of active matrix substrate in which each pixel section has a retention capacitor element. This gives an effect of preventing self-discharge of liquid crystal layer or degradation of pixel signal caused by off-current of TFT or the like during off-state of the TFT or the like. The retention capacitor element is also used as a supply path of various modulation signals for driving liquid crystal.
The following describes concrete examples (eg. Document 1) of known structure of active matrix substrate used for a conventional active matrix liquid crystal display apparatus. FIG. 18 is a schematic plan view showing a single pixel of an active matrix substrate of a conventional active matrix liquid crystal display apparatus.
As shown in FIG. 18, in a conventional active matrix substrate 200, a plurality of pixel electrodes 51 are arranged in matrix, surrounded by scanning signal lines 52 for supplying scanning signals, and data signal lines 53 for supplying data signals, which intersect with each other. Further, a TFT 54 is provided in each intersection of the scanning signal lines 52 and the data signal lines 53. The TFT 54 serves as a switching element connected to the pixel electrode 51. The gate electrode 55 of the TFT 54 is connected to the scanning signal lines 52 through which scanning signals are supplied. In this manner the driving of TFT 54 is controlled. Further, the source electrode 66a of the TFT 54 is connected to the data signal lines 53 through which data signals are supplied. Further, the drain wire 56 is connected to the drain electrode 66b of the TFT 54, the drain wire 56 is also connected to one of the electrodes (retention capacitor upper electrode) 57 of the retention capacitor element, and the retention capacitor electrode 57 is connected to a pixel electrode 51 via a contact hole 58. A retention capacitor (common) wire 59 serves as the other one (retention capacitor lower electrode) of the two electrodes of the retention capacitor element.
The liquid crystal display apparatus used for a large-sized liquid crystal TV often adopts a Vertical Alignment (VA) mode having a multi-domain, or so-called a Multi-domain Vertical Alignment (MVA) mode, so as to ensure a wide viewing angle (see Document 2, for example).
In the MVA mode, the pixel electrodes of the active matrix substrate and the counter electrodes of the counter substrate are provided with an exsection pattern or an alignment control projection for adjusting alignment of liquid crystal molecules from which a fringe field is formed. Provision of fringe field has an effect of scattering the liquid crystal molecules so that they are aligned into plural directions. This is how the wide viewing angle is ensured. In this way, the conventional active matrix substrate shown in FIG. 18 ensures a wide viewing angle by having an exsection pattern or an alignment control projection for adjusting alignment of liquid crystal molecules in each of the pixel electrodes of the active matrix substrate and the counter electrodes of the counter substrate. Further, in order to prevent light leak or improve initial response speed after voltage application, there is a technique of embedding electrodes in the portions having the exsection patterns (may be referred also to as electrode slits) of the pixel electrodes and the counter electrodes (see Document 3, for example).
In the manufacturing process of active matrix substrate, foreign bodies or remaining films may cause short-circuit (leak) between the source electrode and the drain electrode of a TFT. In the resulting defective pixel, the pixel electrodes cannot be given proper voltages (drain voltages). As a result, some defective spot such as a luminescent spot or a black spot occur in the display screen of the liquid crystal display apparatus. This results in a decrease in yield of manufacturing.
In view of this problem, there is a technique for forming a correction connection wiring in advance between each of an adjacent pair of pixels (see Document 4, for example). In the case of pixel defect, this technique carries out laser irradiation with respect to the correction connection wiring so as to allow the pixel electrode of the defective pixel to be electrically conducted to the pixel electrode of the adjacent pixel. In this way, the voltage equal in potential to that of the adjacent pixel is supplied to the defective pixel, and the defective pixel is driven by a pseudo operation.
However, this method needs to be improved to solve the following problem. Normally (in normal operation), the pixels are insulated with each other, and therefore the correction connection wirings are required to be formed across the pixels. Therefore, as the area of the correction connection wiring increases, the aperture ratio decreases. Further, in the sporadic short-circuit (leak) between the source electrode and the drain electrode of the TFT, it is preferable to compensate the error within the pixel in which the defect occurs. This is because, if the defective pixel is driven by the TFT of the adjacent pixel via the correction connection wiring after the leakage portion is cut off, an extra driving load is exerted on the TFT of the adjacent pixel. However, in the foregoing pixel defect correction method, the defect of the pixel can be corrected only by connecting adjacent pixels. Therefore, the correction within the pixel concerned was not possible. Suggested to solve this problem of TFT defect is a redundant structure of liquid crystal display apparatus. In the redundant structure, a plurality of TFTs is connected in parallel with respect to a single pixel (see Document 5, for example).
[Document 1]
Japanese Unexamined Patent Publication Tokukaihei 09-152625/1997 (published on Jun. 10, 1997)
[Document 2]
Japanese Unexamined Patent Publication Tokukai 2001-83523/2001 (published on Mar. 30, 2001)
[Document 3]
Japanese Unexamined Patent Publication Tokukai 2001-117083/2001 (published on Apr. 27, 2001)
[Document 4]
Japanese Unexamined Patent Publication Tokukaihei 02-135320/1990 (published on May 24, 1990)
[Document 5]
Japanese Unexamined Patent Publication Tokukaihei 07-199221/1995 (published on Aug. 4, 1995)